The present invention relates to an electronic apparatus which can be driven by a battery and to which a serial bus having a data line and a power supply line is connected if necessary.
In recent years, various electronic apparatuses that can be driven by a battery have been developed. Also, various electronic apparatuses that can receive data from other electronic apparatuses and can transmit data thereto have been developed.
In most electronic apparatuses of these types, the battery (secondary battery) is charged with the power supplied from a commercial power supply through an adapter designed for charging the battery.
Various types of interfaces are available for achieving data communication between electronic apparatuses. High-speed serial interfaces, such as IEEE1394, have been standardized in the computer industry. A serial interface is a serial bus that has a data line and a power-supply line. Not only can data be transferred through the data line, but also power can be supplied through the power supply line. Further, the data representing the amount of power that can be supplied or that has been requested can be supplied through the data line from one electronic apparatus to another.
In the conventional battery-driven electronic apparatus, the battery is charged by using the commercial power supply, as has been described above. Hence, the serial bus having a data line and a power supply line is used only as a data line for high-speed data transfer. The power supply line cannot be said to be utilized effectively.